Hydrocarbon waxes have been finding use in various applications including ink, paints, emulsions, and releasing agents for toner. In addition, the hydrocarbon waxes may be used in applications except those described above, and examples of the applications include resin modifiers, components for tackiness agents, components for adhesives, components for lubricant oils, organic or inorganic composite materials, heat storage materials, modifiers for fuel oils such as a light fuel oil, modifiers for asphalt, high performance waxes, and cosmetics.
Various properties are requested of each of the hydrocarbon waxes to be used in those applications, and examples of the properties include: reduced tackiness and reduced bleedout; a moderately low melting point (20 to 80° C.); a moderate hardness; and excellent temperature response property. However, it has not been easy to meet levels desired for those properties simultaneously because each of the properties is susceptible to the molecular weight, molecular structure, and the like of each of the waxes.
For example, the melting point of a paraffin wax as one kind of the hydrocarbon waxes can be lowered to about 50° C. by adjusting the weight average molecular weight (Mw) of the paraffin wax to less than 1,000. However, the paraffin wax involves the following problem: the paraffin wax is soft, in other words, has a low hardness.
In addition, other kinds of the hydrocarbon waxes are, for example, polyolefin waxes. However, none of the polyolefin waxes has sufficient properties with reference to the properties requested in the above applications.
For example, Patent Document 1 discloses a process for the production of a polyolefin wax using a metallocene catalyst. However, a polypropylene wax described in an example of the document has a relatively high molecular weight, and hence has a high melting point. Patent Documents 2 and 3 each disclose a process for the production of an olefin oligomer by cationic polymerization. However, the molecular weight and stereoregularity of a polymer to be obtained are hard to control in the cationic polymerization, so the resultant polymer does not have such sharp melting property as to melt only at a specific melting point (excellent temperature response property), and the absence of such property is responsible for the tackiness or bleedout of the polymer. Patent Document 4 discloses a process for the production of a polyolefin wax using a specific metallocene catalyst. However, the polyolefin wax is a polymer produced mainly from ethylene or propylene and having a weight average molecular weight (Mw) of 1,000 or more, and hence has a high melting point. Patent Document 5 discloses a process for the production of a polyolefin using a metallocene catalyst. However, a 1-olefin having a relatively low molecular weight such as propylene or hexene is used in an example of the document, and the use of a polyolefin made of any such olefin as a wax may involve the following difficulty: it is difficult to solve problems concerning the tackiness and bleedout of the wax, and a problem concerning the melting point of the wax simultaneously. Patent Document 6 discloses an α-olefin polymer using an α-olefin having 18 carbon atoms as a raw material, and the polymer has the following preferable properties suitable for use as a wax: a weight average molecular weight (Mw) of 4,000 and a melting point of 39° C. However, the technique described in Patent Document 6 has not sufficed for the following object: the wax is improved in accordance with its applications so that specific property may be changed.
As described above, it has not been easy to meet various requested properties in a balanced manner, and at the same time, to change specific property freely in accordance with each application with any one of the conventional techniques concerning the hydrocarbon waxes, and hence additional technical development has been demanded.
Patent Document 1: JP 03-100004 A
Patent Document 2: JP 05-222120 A
Patent Document 3: JP 2000-159832 A
Patent Document 4: JP 06-293805 A
Patent Document 5: JP 07-507352 A
Patent Document 6: WO 05/073242